It has been years since I read any of those, but the first several books had him literally shoving tentacles into their vajayjays so that they orgasmed over and over and didn't have the energy to bother him anymore. Pretty sure it was fairly graphic too, but again, it has been a while. Also, iirc, one demon had a dick (even though female) and constantly fucked the other demon.
Fuck, lemme go find the actual documents I downloaded to Calibre.
Well, found this at least: "The fiend then gave up on worrying about the silly box and resumed pounding the face-down-ass-up succubus’s tight asshole with renewed vigour."
If I found that quickly, I'm fairly certain there are a hundred others throughout the books.